Mobile cantilevered bridge scaffold



July 22, 1969 a. J. PRICE MOBILE GANTILEVERED BRIDGE SCAFFOLD 3 Sheets-Sheet 1 Filed May 1, 1967 I L ux L\ m Z N/ WE V! a B TTO/QNE July 22, 1969 a. J. PRICE 3,456,756

MOBILE GANTILEVERED BRIDGE SCAFFOLD Filed May 1, 1967 3 Sheets-Sheet 2 INVENTOR.

B/LLy JFK/ca Y July 22, 1969 B. J. PRICE MOBILE CANTILEVERED BRIDGE SCAFFOLD 3 Sheets-Sheet 5 Filed May 1, 1967 m5 mm W. J V! a B fif FTTOENE) US. Cl. 18263 4 Claims ABSTRACT OF THE DISCLOSURE A mobile chassis adapted to move along the edge of a bridge deck, a cantilevered platform member pivotally mounted to the chassis, and double-acting means mounted upon the chassis and connected to the platform member for positively swinging the platform member beneath and away from the bridge deck.

BACKGROUND OF THE INVENTION This invention relates to a bridge scaffold, and more particularly to a mobile bridge scaffold pivotally supporting a cantilevered platform.

In bridge construction, and particularly the construction of reinforced concrete bridges, a certain amount of manual labor has to be performed beneath the bridge deck after it is constructed. For a concrete bridge deck, the forms must be stripped from beneath the deck after the concrete has set. Moreover, a certain amount of finishing work must be performed beneath the bridge deck, such as finishing the concrete or painting the steel supporting members, such as the truss Work.

In order to accomplish this manual labor beneath the bridge deck, various types of scaffolds have been designed and constructed to provide a platform beneath the bridge deck upon which workers may carry out these finishing operations. Some platforms have been of a temporary, stationary type, which require about as much time in assembling and positioning, and dis-assembling, as the actual work performed by the men on the scaffold. Other types of bridge scaffolds have been mounted on mobile chassis for movement longitudinally of the bridge as the work beneath the bridge deck progresses, such as disclosed in the Kaufman Patent 2,669,490 and the Sims Patent 3,035,659. These patents also disclose mobile scaffolds incorporating cantilevered platforms which are moved into operative position beneath the bridge deck and to an inoperative position away from the bridge deck, by various types of cable and winch means with the assistance of gravity.

SUMMARY OF THE INVENTION This invention contemplates not only a bridge scaffold incorporating a mobile chassis and a pivotally mounted, cantilevered platform, but also fluid-powered means for positively swinging the platform in both directions between its operative and inoperative positions.

The invention also contemplates a mobile cantilevered bridge scaffold incorporating a particular construction of the framework and hinge means for pivotally swinging the platform relative to the chassis and the bridge deck with a minimum of effort and maximum efficiency.

Another object of this invention is to provide in a cantilevered bridge scaffold a pivotal connection between the movable platform member and the supporting chassis in which the pivotal axis is located substantially above the chassis to provide a large radius and a small arc through which the platform swings, and to improve the leverage of the means for swinging the platform member between its operative and inoperative positions.

A further object of this invention is to provide a mobile nited States Patent cantilevered bridge scaffold in which the mobile chassis will occupy a minimum of space transversely of a bridge deck, and in which the chassis may simultaneously support a cantilevered platform extending the full width of the deck.

Another object of this invention is to provide in a mobile cantilevered bridge scaffold a platform incorporatiing foldable platform extensions so that the platform with the extensions folded may be moved into operative position between relative narrow bridge supporting members and the platform extensions may be unfolded in operative pos1tion.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an end elevation of the bridge scaffold made in accordance with this invention in operative and inoperative positions upon a bridge;

FIG. 2 is an enlarged end elevation of the scaffold in operative position, with the bridge disclosed in phantom;

FIG. 3 is a top plan view of the scaffold disclosed in FIG. 2;

FIG. 4 is a section taken along the line 44 of FIG. 2; and

FIG. 5 is an enlarged outboard side elevation of the platform disclosed in 'FIG. 4 partially in section.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings in more detail, the scaffold 10 made in accordance with this invention is disclosed in FIGS. 1, 2 and 4 upon a bridge 11 including a concrete deck 12, the lateral edges of which form curbs 13 and 14, and including a center dividing strip 15. The deck 12 is supported by longitudinal I-beam stringers 17. The longitudinal stringers 17 are supported at spaced longitudinal intervals by cross-beams 18 mounted on trusswork 19, carried by concrete piers 20.

The scaffold 10 includes a mobile chassis 22 upon which is pivotally mounted a cantilevered platform member 23.

The chassis 22 is disclosed as a rectangular frame 25 upon which is mounted the various operating equipment, and also for supporting the operator of the scaffold. The chassis 22 is supported for movement longitudinally of the bridge and adjacent one side thereof, for example the curb 13, by running gear, such as 27 and 28, incorporating front wheels 29 and 30 and rear wheels 31 and 32, respectively. The rear wheels 31 and 32 may be driven by any convenient means, such as differentials 33 and 34 by hydraulic motors 35 and 36, respectively. The hydraulic motors 35 and 36 are supplied with hydraulic fluid under pressure from hydraulic pump 38 driven by gasoline engine 40 through fluid lines, not shown. The hydraulic pump 38 is connected to the hydraulic reservoir 41, by fluid lines, not shown, in order to complete the hydraulic circuit. The chassis 22 may also mount other equipment for other purposes, such as an air compressor 42, also driven by the gasoline engine 40.

The chassis 22 also supports an operator station 44, which may take the form of a cab, mounting a control panel 45 and an operator seat 46.

As particularly disclosed in FIGS. 1 and 2, the outboard end of the chassis 22 projects laterally beyond the outboard running gear 27 sufficiently to extend beyond the curb 13 of the bridge deck 12.

Fixed to and projecting upwardly from the chassis frame 25 adjacent the outboard end of the chassis 22 is a side frame 48 of the same width as the frame 25.

The platform member 23 includes an elongated platform 50 having a rectangular frame 51 and a platform deck 52. The platform 50 is sufficiently long to extend beneath the bridge deck 12 transversely any desired distance.

Fixed to and projecting upwardly, preferably at right angles to the platform 50 adjacent its outboard end is a support frame 53, also disclosed as rectangular and of substantially the same width as the platform 50. The support frame 53 is long enough to extend vertically from the platform 50 in operative position above the bridge deck 12, the chassis 22 and the top end of the side frame 48. The top end of the side frame 48 is pivotally connected to the support frame 53 below its top end by one or more journal members 55 having a common pivotal axis, parallel to the direction of travel of chassis 22..In the scaffold two journal members are employed on each side of the frames 48 and 53, although only one journal member 55 including a pivot pin 56 can be seen in the drawings.

The distance between the journal member 55 and the platform is suflicient for the platform 50 to extend transversely beneath the deck 12 in operative position and allow suflicient head room for workers to stand on the platform deck 52 and conveniently Work beneath the bridge deck 12.

Spaced vertically above the journal member and mounted on the upper end of the support frame 53, and on opposite sides thereof, are a pair of clevises 58 and 59 receiving and pivotally connected by pivot pins 60 to the free ends of piston rods 61 and 62. The pivot pins 60' have a common pivotal axis parallel to the pivotal axis of the journal pins 56. The piston rods 61 and 62 are reciprocably received within their corresponding hydraulic cylinders 63 and 64, the lower ends of which are pivotally connected by pivot pins 65 and 66 to the chassis frame 25. The hydraulic cylinders 63 and 64 are doubleacting and are supplied with hydraulic fluid under pressure by fluid lines, not shown, from the hydraulic pump 3-8.

It will be noted that the hydraulic cylinders 63 and 64 and the corresponding piston rods 61 and 62 are disposed in normal operative position at approximately a 45 angle to the chassis frame '25 to obtain optimum leverage. The are of travel of the pivot pin 60 between its operative and inoperative positions is disclosed in dashed lines in FIG. 2. Since the maximum turning force transmitted axially through the piston rod 61 must act tangentially to the illustrated are generated by the pivot pin 60, then it is apparent that the positioning of the cylinder 63, piston rod 61 and pivot pin 60 is more efficient than a cylinder mounted upon and parallel to the chassis frame 25. In order to obtain the optimum angular position of the cylinder 63 and piston rod 61, the pivot pin 60 is located above the journal pin 56 and the journal pin 56 is mounted above the chassis frame 25. In this manner, the maximum components of forces exerted axially through the piston rod 61 will turn or pivot the platform support frame 53 and a minimum of the force components will be lost or wasted in acting parallel to the longitudinal axis of the support frame 53, during the entire stroke of the piston rod 61.

The journal member 55 is mounted on top of a vertically extending side frame 48 in order to elevate the pivotal axis of the platform. member 23 as much as possible to provide a maximum radius and a minimum pivotal are through which the platform member 23 travels between its operative and inoperative positions.

Although FIG. 1 discloses the inoperative position of the platform member 23 in phantom at a pivotal angle slightly less than 90 from the operative position of the platform member, nevertheless the inoperative position could be at a much smaller angle with the free end of the platform 50 still clearing the trusswork 19.

Mounted on the inboard end of the carrier frame 25 is a counterweight 70', disclosed as a massive block of concrete, in order to assure that the center of gravity of the entire scaffold 10 extends between the running gears 27 and 28, regardless of the pivotal position of the platform member 23. It is also within the scope of this invention to provide a platform 50 long enough to substantially span the entire width of the bridge deck 12 without extending the corresponding dimension of the carrier frame 25, by providing sufiicient mass within the counterweight 70. In this manner, the platform member 50 will extend far enough for the workmen to complete their finishing operation upon the entire width of the bridge for each station of the scaffold 10 along the bridge. Since the corresponding transverse dimension of the chassis 22 does not have to be extended, there will be sufficient clearance on top of the bridge deck 12 for at least one lane of moving traffic as disclosed in FIG. 1.

As best disclosed in FIGS. 3, 4 and 5, platform extensions 73 and 74, preferably rectangular, are pivotally connected along their inner edges by hinge pins 75 and 76 to the opposite side edges of the platform 50. In their normal operative positions disclosed in solid lines in FIGS. 4 and 5, the extensions are folded outwardly substantially coplanar to each other and the platform 50- to provide an expanded platform surface beneath the bridge deck 12. When not in use, the platform extensions 73 and 74 are folded upwardly and inwardly to their inoperative positions as disclosed in phantom in FIG. 5. The purpose of these platform extensions 73 and 74 is to permit the platform 50 to move between closely spaced truss members in the trusswork 19 with the extensions 73 and 74 folded in inoperative position. Then, when the platform 50 is in operative position, the extensions are unfolded to provide maximum platform surface, beneath the deck 12.

In order to assist in supporting the platform 50 beneath the bridge deck 12 in operative position, a suspension member 78 may be mounted on each side of the platform frame 51. Suspension member 78 is provided With a pair of opposed clamp jaws 79 pivotally connected by pin 80 and adapted to engage the bottom flange of one of the I-beams 17 in operative position, and to be locked in that position by a locking pin 81. The clamp jaws 79 may then be tightened against the bottom flange of the I-bearn 17 by a ratchet member 82. The suspension member 78 may be of particular benefit for especially long platforms 50.

As an additional safety feature, a locking rod may be permanently pivotally connected to the bottom of the carrier frame 25 by pivot pin 86. When the platform member 23 is in operative position, then the free end of the locking rod 85 may be fitted within the clevis 87 fixed to the support frame 53 and locked in place by a locking pin 88. When it is desired to move the platform member 23 away from its operative position, the locking pin 88' is of course first removed.

It is therefore apparent that a mobile cantilevered bridge scaffold of simple and economical construction has been developed which can be positively and quickly pivoted between its operative and inoperative positions with a minimum hydraulic stroke, a maximum radius and gradual arc of travel for the platform member through a relatively small pivotal angle, and with an optimum application of a turning force by the hydraulic drive means upon the platform member.

It will be apparent to those skilled in the art that various changes may be made in the invention without departing from the spirit and scope thereof, and therefore the invention is not limited by that which is shown in the drawings and described in the specification, but only as indicated in the appended claims.

What is claimed is:

1. A mobile bridge scaffold comprising:

(a) a chassis having an outboard edge and an inboard edge,

(b) running gear mounted on said chassis to support said chassis for travel along the upper surface of and adjacent and parallel to one edge of a bridge deck so that said outboard edge projects laterally outboard of said deck edge,

(c) a side frame fixed to and projecting above said chassis adjacent said outboard edge,

(d) an elongated platform having an outboard end and a free inboard end,

(e) an elongated support frame fixed to said outboard 5 end and extending above said platform in operative position,

(if) journal means connecting said support frame to said side frame for pivotal movement of said platform in a substantially vertical plane between an operative position in which said platform is spaced far enough below said chassis that said platform will extend transversely beneath the bridge deck and have suflicient head room to permit workmen to stand on said platform, and an inoperative position in which the platform is laterally outboard of the bridge supporting structure to permit free movement of the chassis along said deck,

(g) an elongated rod pivotally connected to said support frame above said journal means in operative 20 position, and

(h) double-acting drive means mounted on said chassis for reciprocably and longitudinally moving said rod to positively swing said platform in either direction between said inoperative and operative 25 positions. 2. The invention according to claim 1 in which said double-acting drive means comprises a fluid cylinder,

means pivotally connecting said cylinder to said chassis below said journal means, said rod comprising a piston rod reciprocably received in said cylinder.

3. The invention according to claim 1 in which the inboard end of said platform projects, in operative position, inboard substantially farther than the inboard end of said chassis, and further comprising a counter-weight mounted on said chassis adjacent said inboard edge to maintain the center of gravity of said scaffold within said running gear for any position of said platform.

4. The invention according to claim 1 further comprising suspension means pivotally connected to said platform adjacent said inboard end for connection to a structural portion of said bridge beneath the deck to assist in supporting the free end of said platform in operative position.

References Cited UNITED STATES PATENTS 2,196,511 4/1940 Wagner 18262.5 2,241,275 5/1941 Shinn 182-63 2,669,490 2/1954 Kaufman 182-63 REINALDO P. MACHADO, Primary Examiner US. Cl. X.R. 182-14l 

